Exponentially weighted moving averaging filter with adjustable weighting factor

ABSTRACT

A method of increasing a weighting factor of an exponentially weighted moving averaging (“EWMA”) filter is provided. The method includes monitoring a data stream containing raw data values, and determining an EWMA value based on the data stream by an electronic control module. The method includes determining if the EWMA value is between a predetermined maximum fault threshold value and a predetermined minimum fault threshold value. The method includes increasing the weighting factor of the EWMA filter to more heavily weigh incoming raw data values of the data stream based on the difference between the first raw data value and a previously calculated filtered value exceeding the calibration value.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application claims priority to U.S. Provisional PatentApplication Ser. No. 61/718409 filed on Oct. 25, 2012 which is herebyincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

Exemplary embodiments of the invention relate to a system and method ofincreasing a weighting factor of an Exponentially Weighted MovingAveraging (“EWMA”) filter and, more particularly, to a system and methodof increasing a weighting factor to more heavily weigh incoming raw datavalues of a data stream.

BACKGROUND

Exponentially Weighted Moving Averaging (“EWMA”) filtering is a dataprocessing technique used to reduce the variability of an incomingstream of data that is monitored over a period of time. A EWMA filtercalculates an averaged or filtered value that is based on raw datapoints collected from the incoming stream of data. In one approach, EWMAfiltering may be used to filter data collected by a nitrogen oxidesensor (“NOx”) sensor. The NOx sensor may be located within an exhaustgas conduit of an exhaust gas treatment system, and is used to generatea signal that is indicative of the level of NOx in exhaust gas emittedfrom an internal combustion engine. The EWMA filter monitors the datacollected by the NOx sensor to determine a filtered value.

In the event the filtered value determined by the EWMA filter exceeds amaximum threshold value or is below a minimum threshold value during adiagnostic test, a diagnostic trouble code (“DTC”) may be set to a failstatus. The fail status indicates that there may be an issue with theNOx sensor (e.g., an element in the sensor is cracked, or contaminated),and a malfunction indicator light (“MIL”) may be illuminated to indicatethe fault. Corrective action may be taken to repair or replace the NOxsensor. However, if the fail status stored in the vehicle computer isnot manually cleared after the corrective action, the MIL light willeventually be turned off or deactivated after the filtered valuedetermined by the EWMA filter is below the fault threshold value, andthe diagnostic test is passed a predetermined number of times.Specifically, some types of regulations require that the diagnostic testpasses for three key or ignition cycles before the MIL is allowed todeactivate at the beginning of the fourth key cycle.

EWMA filtering may delay deactivating the MIL. This is because EWMAfiltering tends to place significant emphasis on relatively older datacollected from the NOx sensor that indicates the fail status. Thus, thefiltered value calculated by the EWMA filter may exceed the thresholdvalue even after the NOx sensor has been repaired or replaced.Accordingly, it is desirable to provide an approach for EWMA filteringthat provides a filtered value with increased accuracy.

SUMMARY OF THE INVENTION

In one exemplary embodiment of the invention, a method of increasing aweighting factor of an exponentially weighted moving averaging (“EWMA”)filter is provided. The method includes monitoring a data streamcontaining raw data values, and determining an EWMA value based on thedata stream by an electronic control module. The method includesdetermining if the EWMA value is between a predetermined maximum faultthreshold value and a predetermined minimum fault threshold value. Themethod includes increasing the weighting factor of the EWMA filter tomore heavily weigh incoming raw data values of the data stream based onthe difference between the first raw data value and a previouslycalculated filtered value exceeding the calibration value. In oneembodiment, the weighting factor is determined empirically.

The above features and advantages and other features and advantages ofthe invention are readily apparent from the following detaileddescription of the invention when taken in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features, advantages and details appear, by way of example only,in the following detailed description of embodiments, the detaileddescription referring to the drawings in which:

FIG. 1 is an exemplary schematic diagram of a diagnostic systemincluding a sensor and a control module;

FIG. 2 is a graph illustrating raw values collected by the sensor inFIG. 1 and averaged or filtered values calculated by an EWMA filter; and

FIG. 3 is a dataflow diagram of the control module shown in FIG. 1.

DESCRIPTION OF THE EMBODIMENTS

The following description is merely exemplary in nature and is notintended to limit the present disclosure, its application or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features. Asused herein, the term module refers to an application specificintegrated circuit (ASIC), an electronic circuit, a processor (shared,dedicated, or group) and memory that executes one or more software orfirmware programs, or a combinational logic circuit.

Referring now to FIG. 1, an exemplary embodiment is directed to adiagnostic system 10 for an exhaust gas treatment system 12 including anexhaust gas conduit 20, a nitrogen oxide (“NOx”) sensor 22, amalfunction indicator lamp (“MIL”) 26 and a control module 30. Thecontrol module 30 is in communication with the NOx sensor 22 and the MIL26. The NOx sensor 20 monitors an exhaust gas 32 produced by an internalcombustion engine (not shown), and generates a signal indicative of alevel of NOx in the exhaust gas 32. The control module 30 monitors theNOx sensor 22 to determine the level of NOx in the exhaust gas 32. Thecontrol module 30 uses an exponentially weighted moving averaging(“EWMA”) filter 36 to reduce the variability of a stream of data that iscollected over a period of time by the NOx sensor 22.

It should be noted that while FIG. 1 illustrates the control module 30monitoring a NOx sensor 22, the diagnostic system 10 may be applied toany type of diagnostic system that uses EWMA filtering to reduce thevariability of raw data that is collected over a period of time. Forexample, the diagnostic system 10 may be used to filter catalyst testdata from a device such as, for example, a selective catalytic reduction(“SCR”) device. Some other examples of the diagnostic system 10 mayinclude an air quality system.

In one embodiment, the NOx sensor 22 generates a pumping current ratiosignal to indicate whether the NOx sensor 22 is functioning as intended.The pumping current ratio is based on the amount of current needed topump 1000 ppm of oxygen (“O₂”) into a chamber (not shown) of the NOxsensor 22, and indicates if the NOx sensor 22 has faulted. For example,if the pumping current ratio is relatively high, this may indicatecontamination of the NOx sensor 22, and if the pumping current ratio isrelatively low, this may indicate a cracked NOx sensor 22. The EWMAfilter 36 receives, as input, the pumping current ratio signal from theNOx sensor 22. The pumping current ratio signal is a raw data valuecollected by the NOx sensor 22 over a period of time. The EWMA filter 36determines averaged or filtered pumping current ratio values based onthe raw data.

FIG. 2 is an exemplary graph illustrating a stream of raw values 40(e.g., the pumping current ratio (PCR) signal) collected over a periodof time t by the NOx sensor 22 (FIG. 1). Each raw value 40 representsthe results of a diagnostic test (e.g., each raw value 40 represents theresults of one diagnostic test, and the graph in FIG. 2 is anillustration of twelve different diagnostic tests). In one embodiment,the control module 30 (FIG. 1) performs a self-diagnostic test bydetermining if the pumping current ratio signal generated by the NOxsensor 22 indicates a fault within the NOx sensor 22. The EWMA filter 36(FIG. 1) determines averaged or filtered values 42 based on the rawvalues 40. The graph also illustrates a maximum fault threshold value50, a maximum re-pass threshold 52, a worst performing acceptable(“WPA”) maximum level 54, a WPA nominal level 56, a WPA minimum level58, a minimum re-pass value 57, and a minimum fault threshold value 59.

Referring now to both FIGS. 1-2, the maximum fault threshold value 50represents the minimum pumping current ratio value required to trigger afault in the control module 30 indicating a fault due to an elevatedpumping current ratio such as, for example, contamination of the NOxsensor 22. Specifically, in the event a specific filtered value 42,determined by the EWMA filter 36, exceeds the level indicated by themaximum fault threshold value 50 during a diagnostic test, a diagnostictrouble code (“DTC”) may be set to a fail status by the control module30. The failed status indicates that a fault within the NOx sensor 22may have occurred, and therefore the MIL 26 may be illuminated by thecontrol module 30. The maximum re-pass value 52 represents the filteredvalue 42 that the EWMA filter 36 is required to generate before thecontrol module 30 may reset the DTC to a pass status after the filteredvalue 42 has exceeded the maximum fault threshold value 50 and the failstatus has been set.

The WPA maximum level 54, the WPA nominal level 56, and the WPA minimumlevel 58 represent a range of acceptable raw values 40 that may be usedby control module 30 during a diagnostic test to determine a pass statusresult during a diagnostic test. Specifically, any raw value 40 thatexceeds the WPA maximum level 54 or that is less than the WPA minimumlevel 58 may not be used by the control module 30 to determine if thepumping current ratio indicates a fault in the NOx sensor 22 (FIG. 1).The minimum fault threshold value 59 represents the minimum pumpingcurrent ratio value required to trigger a fault in the control module 30indicating the pumping current ratio has fallen to a relatively lowlevel, and may indicate the NOx sensor 22 is cracked. In the event aspecific filtered value 42 determined by the EWMA filter 36 is less thanthe level indicated by the minimum fault threshold value 59 during adiagnostic test, a DTC may be set to a fail status by the control module30. The minimum re-pass value 57 represents the filtered value 42 thatthe EWMA filter 36 is required to generate before the control module 30may reset the DTC to a pass status after the filtered value 42 hasdropped below the minimum fault threshold value 59 and the fail statushas been set.

Referring now to FIG. 3, a dataflow diagram illustrates variousembodiments of the diagnostic system 10 that may be embedded within thecontrol module 30. Various embodiments of the diagnostic system 10,according to the present disclosure, may include any number ofsub-modules embedded within the control module 30. As can beappreciated, the sub-modules, shown in FIG. 3, may be combined and/orfurther partitioned to monitor the NOx sensor 22 (FIG. 1). Inputs to thecontrol module 30 may be received from the NOx sensor 22 (FIG. 1),received from other control modules (not shown), and/ordetermined/modeled by other sub-modules (not shown) within the controlmodule 30. In various embodiments, the control module 30 includes theEWMA filter 36, a diagnostic module 60, a raw value difference module62, a WPA module 64, a EWMA weighting factor module 66, a testing module68, and a diagnostic reporting module 69.

The EWMA filter 36 receives, as input, a raw value 40 that representsthe pumping current ratio signal that is currently being detected orobserved by the NOx sensor 22 (FIG. 1). In the approach as discussed,the raw value 40 represents the pumping current ratio signal detected bythe NOx sensor 22 (FIG. 1) at an observation time of t=t₀ (FIG. 2). Theraw value 40 currently detected is illustrated in FIG. 2 as raw value 40_((t0)). The EWMA filter 36 determines a filtered value 42, which isillustrated in FIG. 2 as the filtered value 42 _((t0)). The currentfiltered value 42 is based on the raw value 40 detected at theobservation time of t=t₀, as well as filtered values 42 that have beenpreviously calculated by the EWMA filter 36. Specifically, the filteredvalue 42 may be determined by Equation 1:

EWMA(t ₀)=λY _(t0)+(1−λ)(EWMA)_(t−1) . . . (1−λ)(EWMA)_(t−n)  (Equation1)

for t=1, 2, . . . nwhere EWMA is the filtered value 42 being calculated at the observationtime of t=t₀, λ is a current weighting factor, Y_(t0) is the raw value40 that is being inputted into the EWMA filter 36 at the currentobservation of time t=t₀, (EWMA)_(t−1) is a previously calculatedfiltered value 42 at the last observation time of t=t−1, and n is thenumber of observations.

The diagnostic module 60 receives, as inputs, the current filtered value42 (or an adjusted filtered value 90, which is discussed below) from theEWMA filter 36. The diagnostic module 60 performs a diagnostic test bycomparing the current filtered value 42 to the maximum fault thresholdvalue 50 and the minimum fault threshold value 59. In the event filteredvalue 42 is greater than the fault threshold value 50 or less than theminimum fault threshold value 59, this is an indication that thediagnostic test has not passed, and a fault threshold signal 82 isgenerated by the diagnostic module 60 indicating a fail status.

The diagnostic module 60 may also generate a signal 80 that sets the DTCstatus to fail once the diagnostic test has not passed. For example,referring to FIGS. 2-3, the signal 80 would be set by the diagnosticmodule 60 at the observation time of t=t−1, as the filtered value 42generated by the EWMA filter 36 has exceeded the maximum fault thresholdvalue 50.

The raw value difference module 62 receives, as inputs, the raw value 40from the NOx sensor 22 (FIG. 1) and the fault threshold signal 82 fromthe diagnostic module 60. If the fault threshold signal 82 is received,the raw value difference module 62 compares a difference between the rawvalue 40 currently detected (e.g., at the current observation time oft=t₀) and a previously determined previously calculated filtered value42 measured at the last observation of t=1 that is saved in memory. Theraw value difference module 62 determines if the difference between theraw value 40 (at the current observation time of t=t₀) and thepreviously determined previously calculated filtered value 42 (at thelast observation time of t=t−1) are greater than a calibration value C.This may be expressed by Equation 2:

(EWMA)_(t−1)−raw value_((t0)) >C  (Equation 2)

where (EWMA)_(t−1) is the previously calculated filtered value 42 at thelast observation time of t=t−1 (42 _((t−1)) ) and the raw value_((t0))is the raw value 40 measured at the current observation time of t=t₀ (40_((t0))) shown in FIG. 2).

The calibration value C is a predetermined value, which generallyindicates the pumping current ratio indicated by the filtered value 42at t=t₀, is not within a passing range and may either exceed the maximumthreshold value 50 or may be below the minimum threshold value 59. Inthe event the difference between the previously calculated filteredvalue (EWMA)_(t−1) and the raw value_((t0)) is greater than thecalibration value C, the raw value difference module 62 generates acalibration signal 84.

The WPA module 64 receives, as input, the raw value 40 and thecalibration signal 84. In the event the WPA module 64 receives thecalibration signal 84 from the raw value difference module 62, the WPAmodule 64 compares the raw value 40 with the WPA maximum level 54 andthe WPA minimum level 58. If the raw value 40 is less than the WPAmaximum level 54 and greater than the WPA minimum level 58, then the WPAmodule 64 generates a rapid healing logic signal 86. The rapid healinglogic signal 86 indicates that a potential corrective action may haveoccurred, and the NOx sensor 22 (FIG. 1) may have been repaired orreplaced.

The EWMA weighting factor module 66 receives, as input, the rapidhealing logic signal 86 from the WPA module 64. Upon receipt of therapid healing logic signal 86, the EWMA weighting factor module 66 sendsan adjusted weighting factor λ′ to the EWMA filter 36. The value of theadjusted weighting factor λ′ is greater than the value of the currentweighting factor λ used in Equation 1 above. Referring now to FIGS. 2-3,the adjusted weighting factor λ′ will more heavily weight the incomingraw values 40 starting from 40 _((t0)) (e.g., 40 _((t0)), 40 _((t+1)),40 _((t+2)), 40 _((t+3)), and 40 _((t+4)) shown in FIG. 2) duringcalculation of the corresponding filtered values 42 starting at time t0(e.g., 42 _((t0)), 42 _((t+1)), 42 _((t+2)), and 42 _((t+3)) shown inFIG. 2) when compared to the current weighting factor λ. Therefore, whenthe EWMA filter 36 calculates a next filtered value 42 _((t0)) whenrapid healing logic is active, at observation time of t=t0, the filteredvalue 42 _((t0)) generally may produce a value that is below the maximumfailure threshold 50, but still above re-pass value 52. This value wouldstill represent a failing result. However, the next filtered value 42_((t+1)) would indicate a passed result. The new weighting factor λ′ maybe determined empirically, and may be adjusted based on the specificapplication.

The EWMA filter 36 determines the adjusted filtered value 90 based onthe raw value 40 that is detected at an observation time of t=t0 (shownin FIG. 2) using the new weighting factor λ′. Specifically, the adjustedfiltered value 90 may be determined by the following equation:

EWMA(t0)=λ′Y _(t0)+(1−λ′)(EWMA)_(t−1) . . .(1−λ′)(EWMA)_(t−n)  (Equation 3)

where EWMA(t0) is the filtered value 90 being calculated at theobservation time of t=t0, λ′ is the new weighting factor, Y_(t0) is theraw value 40 that is being inputted into the EWMA filter 36 at theobservation of time t=t0, (EWMA)_(t−1) is a previously calculatedfiltered value 42 at the last observation time of t=t−1, and n is thenumber of observations.

The diagnostic module 60 receives, as input, the adjusted filtered value90 from the EWMA filter 36. The diagnostic module 60 performs adiagnostic test by comparing the adjusted filtered value 90 to themaximum fault threshold value 50 and the minimum fault threshold value59. The diagnostic module 60 determines if the adjusted filtered value90 is less than the maximum fault threshold value 50 and greater thanthe minimum fault threshold value 59. If the filtered value 42 is lessthan the maximum fault threshold value 50, this is an indication thediagnostic test has passed, and the diagnostic module 60 generates apassing signal 100 that is sent to the testing module 68. The passingsignal 100 indicates that a diagnostic test performed by the diagnosticmodule 60 has generated a pass status.

The testing module 68 receives, as input, the fault threshold signal 82and the passing signal 100 generated by the diagnostic module 60, aswell as the rapid healing logic signal 86 from the WPA module 64. Uponreceipt of the rapid healing logic signal 86, the testing module 68 willsend an initiate testing signal 102 back to the diagnostic module 60.The initiate testing signal 102 will cause the diagnostic module 60 toperform an increased number of diagnostic tests over a period of time.As a result, the fault threshold signal 82 or passing signal 100 will besent from the diagnostic module 60 to the testing module 68 morefrequently.

The testing module 68 will continue to monitor the diagnostic module 60to determine if a predetermined number of diagnostic tests havecompleted and indicate a pass status (e.g., indicated by the passingsignal 100) over a predetermined number of ignition cycles. If thetesting module 68 determines that the predetermined number of diagnostictests have passed over a predetermined number of drive cycles, then areset signal 110 is sent to the diagnostic reporting module 69. In oneembodiment, the testing module 68 may delay sending the reset signal 110to the diagnostic reporting module 69 until the predetermined number ofdiagnostic tests have been performed over the predetermined number ofdrive cycles. For example, in one embodiment, the testing module 68monitors the diagnostic module 60 for a predetermined number ofdiagnostic tests over three ignition cycles. If the diagnostic tests allgenerate passing results, at the beginning of the fourth ignition cycle,the reset signal 110 is sent to the diagnostic reporting module 69, andthe MIL 26 (FIG. 1) is deactivated.

The diagnostic reporting module 69 receives, as input, the reset signal110 from the testing module 68, and generates a signal 120 updating theDTC status to pass, and the MIL 26 (FIG. 1) is deactivated (e.g., thelight is shut off).

Referring generally to FIGS. 1-3, the diagnostic system 10 replaces thecurrent weighting factor λ with the adjusted weighting factor λ′ if thecontrol module 30 determines a corrective action to the NOx sensor 22has been performed after the NOx sensor 22 indicates a fault. Theadjusted weighting factor λ′ will more heavily weight the incoming rawvalues 40 generated by the NOx sensor 22 when compared to the currentweighting factor λ. Therefore, the EWMA filter 36 is able to account fora relatively sudden change in raw data that is collected from the NOxsensor 22 due to a corrective action being performed. As a result, theEWMA filter 36 is generally able to generate filtered values 42 thatpass a diagnostic test immediately after the NOx sensor 22 generatespassing values (e.g., shown in FIG. 2 as the filtered value 42 _((t+1))at the observation time of t=t+1). Thus, the DTC status may be updatedto the pass status and MIL 26 may be deactivated in less time (e.g.,fewer ignition cycles) when compared to some diagnostic systems that arecurrently available.

While the invention has been described with reference to exemplaryembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiments disclosed, but that theinvention will include all embodiments falling within the scope of theapplication.

What is claimed is:
 1. A method of increasing a weighting factor of anexponentially weighted moving averaging (“EWMA”) filter, comprising:monitoring a data stream containing raw data values and determining anEWMA value based on the data stream by an electronic control moduleincluding operative logic; determining if the EWMA value is between apredetermined maximum fault threshold value and a predetermined minimumfault threshold value; and increasing the weighting factor of the EWMAfilter to an adjusted weighting factor to more heavily weigh incomingraw data values of the data steam based on the difference between thefirst raw data value and a previously calculated filtered data valueexceeding the calibration value.
 2. The method of claim 1, wherein theEWMA filter determines an adjusted filter value based on the formulaEWMA(t0)=λ′Y_(t0)+(1−λ′)(EWMA)_(t−1) . . . (1−λ′)(EWMA)_(t−n).
 3. Themethod of claim 1, further comprising: passing the adjusted filter valueto a diagnostic module.
 4. The method of claim 3, further comprising:comparing the maximum fault threshold value and the minimum faultthreshold value to the adjusted filter value.
 5. The method of claim 3,further comprising: issuing a passing signal if the adjusted filtervalue is less than the minimum fault threshold value.
 6. The methodaccording to claim 1, further comprising: providing a worst performingacceptable (WPA) maximum level, and a WPA minimum level for the EWMAfilter to a WPA module.
 7. The method of claim 1, further comprising:comparing the raw data values to the WPA maximum level and the WPAminimum level; and generating a rapid healing logic signal if the rawvalues are greater than the WPA minimum level and less than the WPAmaximum level, the rapid heaing logic signal indicating existence of apotential corrective action.
 8. A diagnostic system comprising: asensor; an exponentially weighted moving averaging (“EWMA”) filteroperatively connected to the sensor; and a control module operativelyconnected to the EWMA filter, the control module being configured anddisposed to increase the weighting factor of the EWMA filter to anadjusted weighting factor to more heavily weigh incoming raw data valuesof the data stream.
 9. The diagnostic system according to claim 8,wherein the EWMA filter is configured and disposed to establish anadjusted filtered value based on the formulaEWMA(t0)=λ′Y_(t0)(1−λ)(EWMA)_(t−1) . . . (1−λ′)(EWMA) _(t−n).
 10. Thediagnostic system according to claim 8, further comprising: a diagnosticmodule operatively connected to the control module, the diagnosticmodule being configured and disposed to determine if the adjustedfiltered value is between a predetermined maximum fault threshold valueand a predetermined minimum fault threshold value.
 11. The diagnosticsystem according to claim 8, wherein the diagnostic module is configuredand disposed to compare the adjusted filtered value to a maximum faultthreshold value and a minimum fault threshold value.
 12. The diagnosticsystem according to claim 8, further comprising: a worst performingacceptable (WPA) module operatively connected to the control module, theWPA module including aWPA maximum level, and a WPA minimum level for theEWMA filter.
 13. The diagnostic system according to claim 11, whereinthe WPA module is configured and disposed to generate a rapid healinglogic signal if raw data values passing to the EWMA filter are greaterthan the WPA minimum level and less than the WPA maximum level, therapid healing logic signal indicating the existence of a potentialcorrective action of the sensor.
 14. The diagnostic system according toclaim 8, wherein the sensor comprises a NOx sensor.
 15. An exhaust gastreatment system comprising: an exhaust gas conduit; a sensoroperatively connected to the exhaust gas conduit; an exponentiallyweighted moving averaging (“EWMA”) filter operatively connected to thesensor; and a control module operatively connected to the EWMA filter,the control module being configured and disposed to increase theweighting factor of the EWMA filter to an adjusted weighting factor tomore heavily weigh incoming raw data values of the data stream.
 16. Theexhaust gas treatment system according to claim 15, wherein the EWMAfilter is configured and disposed to establish an adjusted filteredvalue based on the formula EWMA(t0)=λ′Y_(t0)+(1−λ′)(EWMA)_(t−1) . . .(1−λ′)(EWMA)_(t−n).
 17. The exhaust gas treatment system according toclaim 16, further comprising: a diagnostic module operatively connectedto the control module, the diagnostic module being configured anddisposed to determine if the adjusted filtered value is between apredetermined maximum fault threshold value and a predetermined minimumfault threshold value.
 18. The exhaust gas treatment system according toclaim 16, wherein the diagnostic module is configured and disposed tocompare the adjusted filtered value to a maximum fault threshold valueand a minimum fault threshold value.
 19. The exhaust gas treatmentsystem according to claim 15, further comprising: a worst performingacceptable (WPA) module operatively connected to the control module, theWPA module including a WPA maximum level, and a WPA minimum level forthe EWMA filter.
 20. The exhaust gas treatment system according to claim19, wherein the WPA module is configured and disposed to generate arapid healing logic signal if raw data values passing to the EWMA filterare greater than the WPA minimum level and less than the WPA maximumlevel, the rapid healing logic signal indicating the existence of apotential corrective action of the sensor.